2018 is slated to become the fourth hottest year in recorded history. A global heat wave has brought about a massive European drought, with crop failures and fires plaguing the continent. It’s also brought about the Mendocino-Complex Fire, which is the largest wildfire in California’s state history, a growing phenomenon made worse by groundwater depletion due to years of decreased precipitation.

In contrast, there has been severe flooding in South and Southeast Asia. Since June, at least 370 people have died due to severe flooding in Kerala state in India. Heavier than normal rainfall is said to have contributed to the catastrophic failure of a saddle dam at the Xe Pian Xe-Namnoy hydropower project in southern Laos, which has flooded numerous villages in Laos and Cambodia, displacing thousands of families and causing death and destruction.

The costs of natural disasters are growing

These types of natural disasters – severe flooding and drought caused by extreme weather patterns – currently lead to about 10,000 deaths and cause more than US$40 billion in damage a year, with the number and extremity of the events is only likely to increase in the future. The agricultural sector is particularly vulnerable, given how dependent productivity is on weather, climate, land, and water. As a result, floods and droughts can cause not only severe economic losses in rural communities, but also undermine food and livelihood security in developing countries. Floods and droughts, along with other kinds of natural catastrophes, are costing us more every year, both financially and in terms of human misery.

And our current approaches to disaster risk management are not sustainable. Instead of investing in disaster prevention and preparedness before catastrophic water related event occurs, approximately 90 percent of financial assistance goes towards emergency response and reconstruction. We need to change this paradigm by investing in disaster risk reduction and improved resilience. Preventing significant losses and preparing people to rebound from extreme weather events is more sustainable, cost effective, and humane.

Enhancing nature to build climate resilience

One way to build resilience in the face of increasing climate uncertainty and water variability is to consider what nature has to offer.

Often, the most successful solutions for dealing with water variability use a combination of man-made (‘grey’) and natural (‘green’) infrastructure. Combining the two forms of infrastructure is effective because it enables societies to use the benefits and services provided by natural ecosystems, while enhancing specific elements with built infrastructure.

Grey infrastructure comes in various forms, among them hydropower dams, built river embankments and sluice gates. Examples of green infrastructure are unaltered wetlands that can absorb and retain surface water, sand dunes that act as flood barriers, or underground water aquifers.

For example, one way to safeguard against urban flooding is to try to get as much water as possible into the ground upstream of cities through a combination of man-made and natural means. This can be achieved by channelling excessive rainwater into natural groundwater aquifers by keeping natural water storage in the landscape and building drainage systems that expedite the process of aquifer recharge. This has the dual purpose of reducing urban flooding while also renewing groundwater resources that can then be exploited during a drought when a lack of rainfall threatens crop security or household water use.

This blog is based in part on IWMI and WLE contributions to Stockholm World Water Week 2018. IWMI and WLE led or participated in over 30 sessions at the 2018 Stockholm World Water Week, along more than 3,600 participants from 133 countries.

A man in UttarPradesh, India, walks along a stream which leads to a man-made pond that channels water into underground aquifers during the wet season. This water can then be pumped and used for irrigation in the dry season.

Prashanth Vishwanathan / IWMI

There is no doubt that modern societies need both green and grey infrastructure working in tandem to maximize benefits and ensure long-term sustainable development. The importance of considering nature-based solutions for water variability management has been globally recognized, with UN Water designating 2018 as the year of Nature for Water, and the World Water Development Report being on the theme of nature-based solutions for water.

The tricky thing about these interventions is getting the balance correct. Too much built infrastructure can threaten the effectiveness of services provided by ecosystems. At the same time, nature can’t do it alone. As such, we need to build resilience through an effective portfolio of both grey and green infrastructure that neither undermines, nor depends too heavily on, natural water management systems.

Nature-based solutions don’t fit in spread sheets

Understanding how nature-based solutions can help buffer the effects of natural disasters is complicated; ecosystems are dynamic, responses vary in time and space. Consequently, determining their effects quantitatively, in terms that can be used by planners and engineers, is much more difficult than for built infrastructure.

WLE researchers evaluated the flow regulating functions of natural ecosystems - wetlands, floodplains and woodland - in the Zambezi Basin by simulating the flow of water in the absence of a natural ecosystem and comparing it to the actual flow. This means they looked at the ability of these natural ecosystems to reduce the effects of flooding AND maintain water flow during the dry season. In general, they found that floodplains decrease the amount of water during a flood - or flood flows - while increasing the amount of water that flows during dry spells - or low flows. They also found that headwater wetlands do the opposite, increasing flood flows and decreasing low flows, and the woodland decreases both flood and low flows if it covers 70% of the catchment or more.

However, there were cases where the opposite effects were produced, making it impossible to create a simple correlation between the ecosystem type and the impact on flow regimes. Site-specific factors like topography, climate, soil type, and vegetation all need to be taken into account. This makes determining the impact of green infrastructure, either in isolation or in combination with grey infrastructure, very difficult.

This kind of complexity often keeps policy makers and development planners from considering nature-based solutions, to the great detriment of lives and livelihoods. Although we may not be able to generalize what the effects of nature-based solutions will be in all situations, they can be effective, not only in reducing the immediate negative impacts of water related disasters, but also in improving people’s ability to bounce back after a disaster, especially poor people who are usually more adversely impacted. For instance, through provision of fish, other food and livestock feed, wetlands can, in the aftermath of flooding, help communities cope with transitory food insecurity arising from damage to crops, grazing lands and transport routes.

Why turning to nature still makes sense

While more research is needed, nature-based solutions should nevertheless be a key consideration in future planning and development. Creating a varied portfolio of green and grey infrastructure, both above and below ground, allows for the best environmental, economic and social outcomes, resulting in a system that can absorb shocks and create longer-term security. It reduces the cost of building grey infrastructure, while also protecting the infrastructure that has already been built.

It makes good economic and social sense to protect and enhance our natural systems in order to reduce the impacts of disasters before they happen and help people bounce back after the fact.

We know that nature can’t do it alone, but we also equally know that the effects of allowing the loss or degradation of ecosystems can be devastating. Increasing our knowledge base and understanding of how natural and man-made systems work and interact will allow us to change our practices from reacting to disasters to enhancing resilience to risk before a disaster occurs. Nature may be unpredictable, but it’s worth investing in; ultimately the benefits will surely outweigh the costs of neglecting to do so.

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In an era of rampant land development and increasing climate unpredictability, the world is growing used to alarming images of flooded city streets. But cities can combat these floods by turning themselves into "sponge cities".

Menghoin, H. 2018. Coping with Changes in access to biodiversity and natural resources along the Mekong mainstream and tributaries. Water Knowledge #5. Vientiane, Lao PDR, CGIAR Research Program on Water, Land and Ecosystems

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The views and opinions expressed in this blog are strictly those of the author of each post. They do not represent the opinions of the CGIAR Research Program on Water, Land and Ecosystems (WLE) or of the International Water Management Institute (IWMI) or any associated partners. This is an open space for constructive scientific discussion. If you disagree with the opinions or information displayed, please leave a comment or write to the editor: wle(at)cgiar.org.